The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hybrid powertrains typically include a first torque generator, such as an internal combustion engine (ICE), and a second torque generator, such as an electric machine (EM), each providing torque to a driveline to propel a vehicle. In a full hybrid powertrain, the EM drives the driveline directly without transferring torque through a component of the ICE. In a mild hybrid powertrain, the EM is typically coupled with the ICE through an accessory drive such that torque generated by the EM is transferred to the driveline through the ICE. An exemplary mild hybrid powertrain includes a belt alternator starter (BAS) system. In the BAS system, the EM is coupled to the ICE via a traditional belt and pulley configuration that drives vehicle accessories such as pumps and compressors.
Powertrain torque control typically includes axle torque and propulsion torque control domains. In the mild hybrid powertrain, the propulsion torque is the output torque at the crankshaft of the ICE. This output torque includes the EM torque contribution.
Powertrain torque control typically monitors and adjusts predicted torque and immediate torque. Predicted torque is a slow changing set point of the system. For example, a typical predicted torque request may include driver input. In a spark ignited system, the predicted torque value controls the airflow. In diesel or electric systems, the predicted torque value is shaped to establish a normal operating point of the system according to driver preference. Conversely, immediate torque is a fast changing set point of the powertrain system. Immediate torque is only active when a torque intervention is active. In a spark ignited system, the immediate torque value controls the spark and fuel. In a diesel or electric system, the immediate torque value controls the actual torque produced by the system.
Mild hybrid powertrain control typically provides an EM torque command while commanding the ICE torque actuators directly. Mild hybrid powertrain control typically does not dynamically compensate the EM torque command to account for a delay in the ICE torque response. Thus, a propulsion torque output may undershoot or overshoot the propulsion torque request.